You can’t give advice…
You are a reasonably experienced and qualified teacher. The observer in your lesson is giving you feedback. A typical pattern would be to tell you what they saw as effective and then what you did less well. There are different ways this may be achieved, such as starting by asking you how you think the lesson went. My view is that none of these will be effective and the basic premise that the observer is able to identify what is good practice and what is less effective is fundamentally flawed.
Let’s imagine that one of the criticisms is about needing to use more groupwork. You may or may not think groupwork is a fundamentally effective strategy or not. This is not about whether a particular method works or not; works or not for the particular context or content being worked on by your class.
The point is that anything the observer says about what might have been more effective is pure conjecture. Fortune telling. Perhaps one should ask the observer who tells you that to do “X” would have been better would be to ask them how they know it would have been better?
The observation process needs to identify questions to form part of the discussion with the teacher about the choices they made and how well *both* observers, teacher and the formal observer, thought the lesson went.
Let me suggest that the teacher, experienced and qualified, knows the class better than the observer can ever do. How the individuals in the class react to this subject content.
The best the feedback discussion can ever do, and should aim to do, is to leave the teacher with some thoughts about the mismatches and agreements between their own observations of how the lesson went and those of the second observer. Perhaps a great piece of evidence would be to look at the test data gathered a while after this lesson and reflect on that.